Roll stabilizing systems are well-known which utilize fins projecting from the sides of the vessel below the water line to counteract the rolling action of the vessel due to wave action. The fins produce a counteracting moment by adjusting the angle of the fins relative to the water flowing past the fins as the ship moves through the water. However, stabilizing systems for reducing pitch have not been generally employed. While pitch stabilizing systems have been heretofore proposed, they have usually involved fins mounted adjacent the bow of the vessel to produce maximum effect. However, the fins located in the bow are subject to pounding forces in heavy seas when the bow lifts out of the water. It has been difficult to provide fins of sufficient size to control pitching motion which could also be made sufficiently strong to withstand the pounding action of the bow lifting free of the water and then plunging back into the water, as the level of the water rises and falls in relation to the bow of the ship. The use of stabilizing fins mounted nearer the stern for stabilizing pitch has also heretofore been proposed. For example, in U.S. Pat. No. 3,760,759 there is described a system for controlling both pitch and roll by a single set of fins positioned toward the stern of the vessel. Because such fins project out from the sides of the vessel, they must be supported in cantilever fashion, which means the fins must be made relatively thick, increasing their drag. The fins, because they project outwardly of the vessel, are subject to damage, particularly during docking of the vessel. The counteracting force of the fins, furthermore, is derived entirely from the forward movement of the vessel through the water, limiting their effectiveness at reduced speeds.